1. Field of the Invention
The present invention relates to a method for producing an ink-jet recording head used for recording by discharging droplets, an ink-jet recording head, a substrate for a recording head, and an ink-jet cartridge, and more specifically, to a method for producing an ink-jet recording head including a filter, the ink-jet recording head, a substrate for the recording head, and an ink-jet cartridge including the recording head.
2. Description of the Related Art
Recently, in order to achieve a reduction in size and a high density of an ink-jet recording head, a method for installing an electric control circuit that drives an element for generating an ink-discharging pressure in a substrate has been proposed. The electric control circuit is installed in the substrate using a semiconductor manufacturing technology. According to such an ink-jet recording head, in order to supply a plurality of discharge ports with ink, the substrate is pierced from the reverse face so that each nozzle communicates with a common ink supply port through the substrate and the ink is supplied to each nozzle from the common ink supply port. U.S. Pat. No. 5,478,606 discloses a method for manufacturing such an ink-jet recording head in which the distance between the element for generating an ink-discharging pressure, the element being used for discharging ink from a discharge port, and the discharge port can be controlled with a very high accuracy. In addition, as disclosed in U.S. Pat. No. 6,139,761, when a silicon substrate is used as a substrate of such an ink-jet recording head, the ink supply port can be formed by anisotropic etching.
One of the expectations required for an ink-jet recording head is preventing dust or foreign matter from infiltrating in nozzles. Such dust or foreign matter may infiltrate into the nozzles during the manufacturing process of the ink-jet recording head. Also, such dust or foreign matter may be sent with the ink and then may infiltrate into the nozzles. In order to solve this problem, a filter is provided in the ink-jet recording head.
For example, according to a recording head disclosed in U.S. Pat. No. 6,264,309, a member in which discharging ports and passages are to be formed is bonded with a silicon substrate including an ink supply port. In the above ink-jet recording head, a resistant material layer used for forming the ink supply port by etching is provided on the surface having a heater, and a plurality of pores is provided through the resistant material layer. Thus, the ink supply port and a filter are formed at the same time. In addition, U.S. Pat. No. 6,543,884 discloses a structure wherein separate ink supply ports corresponding to a plurality of ink-jet chambers are provided.
According to Japanese Patent Laid-Open No. 2000-94700, when an ink supply port is formed on a silicon substrate, a membrane filter is simultaneously formed through an etching resistant mask disposed on one surface opposite to the other surface having a heater by utilizing side etching.
However, according to U.S. Pat. Nos. 6,264,309 and 6,543,884, the recording head is produced by bonding the member in which discharging ports and passages are to be formed with the silicon substrate including the ink supply port. Therefore, dust or foreign matter may infiltrate into nozzles during the bonding process. Furthermore, in the methods disclosed in these patent documents, pores forming a filter are provided through a thin film on the silicon substrate in advance and the ink supply port is formed on the silicon substrate. Accordingly, in these methods, the ink supply port must be formed while pores are open through a stop layer against anisotropic etching, which is disclosed in U.S. Pat. No. 6,139,761. Therefore, when the methods disclosed in the above patent documents are applied to the method disclosed in U.S. Pat. No. 5,478,606, a soluble resin used for forming the passages must be immersed in an etchant used for forming the ink supply port. This process may adversely affect the precision of the head to be produced or the production yield of the head with high precision.
In the method disclosed in Japanese Patent Laid-Open No. 2000-94700, an insulating film composed of, for example, SiO2 or SiN is used as the etching resistant mask. The insulating film (i.e., etching resistant mask) exposed on the reverse face of the silicon substrate is generally formed by sputtering or chemical vapor deposition (CVD). Such an insulating film may be corroded on contact with various types of liquid in the subsequent steps. Also, minute scratches may be formed on the insulating film when the substrate is carried in manufacturing equipment of semiconductors during the production process. Thus, it is very difficult to keep this filter composed of the insulating film without causing any defect until the final product is produced.